There are basically three types of grow lights used in horticulture. These are:
HIGH INTENSITY DISCHARGE LIGHTS. (HID)
These come in two types, Metal Halide (MH) and High Pressure Sodium (HPS)
Metal halide bulbs are designed for plants during their growing cycle. That is, for non-fruiting or non-blooming plants. Metal halide lighting is therefore the best HID choice for the plant’s growing phase.
High Pressure Sodium Lights.
HPS grow lights are used primarily for plants that are in their blooming or fruiting phase. Modern high pressure sodium lighting can, however, be bought, which is enhanced for blue spectrum (for vegetative growth) and for red spectrum (for flowering growth). This means that they can be used throughout the entire growing process for most types of plant.
Dual light Systems.
For optimal performance, switchable systems (400 watt and 1000 watt) and dual light systems (250 watt MH + 250 watt HPS giving 500 watt output, 400 watt MH + 400 watt HPS giving 800 watt output and 400 watt MH + 600 watt HPS giving 1000 watt output) are available. This type of lighting system gives the best all round lighting choice.
MERCURY VAPOUR LIGHTS.
Phosphorous coated to promote both blue and red spectrums these lamps are suitable for both the growing and blooming stages of plant growth. They give off more blue light thaN red and are a cheap way to get started, however the lamp wants replacing every nine months as it can become volatile. Mercury vapour lights cost more to run and maintain compared to HPS, MH or fluorescents.
These lights emit less light than high intensity discharge lights and although they can be used throughout the plant cycle their lack of brightness will produce small yields. The light produced tends to be softer and less damaging to tender young plants. For this reason, the fluorescent light is popular for seedlings and cuttings, an excellent way to establish young plants.
All of the above types of lights use some kind of a ballast system. The one most people are familiar with is the fluorescent light. This has, a small, built in, ballast. It allows the fluorescent tube to build up enough energy to strike, and excite the molecules within the tube, causing light to be given off.
Metal Halide and hps lights are usually run from a remote ballast. This is an external box containing the electronics to pre-heat and run the lamp. It is connected to the lamp holder and to the mains power supply. The ballast used is rated for the lamp wattage and so it is necessary to have different ballasts available for each of the different values of lamp to be used. HID bulbs should be replaced after 12 to 18 months of use. Although HID lamps will continue to light beyond 18 months of use, they will have lost up to 30 percent or more of their lumen output while consuming the same amount of electricity.
MERCURY VAPOUR LIGHTS.
Most of these lamps, up to a value of 500 watts, require no additional ballast. You just screw them into the lamp holder supplied by your supplier.
The grow light reflector or hood is used to direct the light towards your growing area. There are literally hundreds of different designs and makes on the market; however, they all do more or less the same thing. The hood usually has a reflective insert to provide greater light intensity and/or to reduce the amount of light that is double reflected in one area, normally directly under the bulb. (This intense light area, known as the sweet spot, can cause a reduction in plant production and growth, giving rise to uneven cropping). You can either purchase a complete system that includes everything you need to get started, or select your ballast, reflector and bulb, separately.
These innovative gadgets consist of a rail along which the grow light is moved usually by a silent, low wattage, motor. The system allows for the light to pause at the end of its travel before changing direction and returning to its point of origin. The advantage of this idea is that it allows one grow light unit to do the job of two or even three static lights.
A WORD OF WARNING ABOUT LIGHTING.
There are an awful lot of companies out there selling grow lights for the hydroponics enthusiasts. As in all walks of life, there are good and bad suppliers and manufacturers of lighting equipment. Always look for equipment made by a reputable company and backed by an official testing scheme. (For example the C E mark in Europe means that the article is up to European standards of safety and quality).
Cheap, nasty, home made, dangerous grow lights have dogged the hydroponics market for some years. There are these kinds of light and there are proper, professional grade, horticultural, lights on today’s market. The first are often death traps, being cobbled together from the cheapest, obsolete, end of the line components that are usually mis-matched and wrongly configured. To think that these poorly built, badly wired, mis-configured lights are being fitted in damp, humid and sometimes even wet, grow rooms is a very scary thought indeed.
The installation of these poor quality, dangerous, grow lights in your home, where your family lives and plays, is always a very grave risk. All this in the name of a bargain!
Don’t risk your own life or the lives of everybody that lives with you. BUY FROM A REPUTABLE SOURCE
Lighting is possibly the most important decision for indoor horticulture, cheap normally represents a health risk. For the sake of saving a relatively small amount of money, ask yourself is it really worth it?